Valuable documents in cash dispensers are usually detected by means of line cameras which scan in valuable documents line by line in the manner of a flat bed scanner. These detection modules require exact alignment of the valuable documents in respect of the line direction of the image sensor. This can therefore be implemented easily by means of mechanical guiding and centering aids because the latter can be arranged outside the comparatively narrow detection region for detecting a scanned line.
However, such image sensors are comparatively costly, which renders it desirable to detect images by means of conventional video or matrix cameras, given that the latter can be obtained cost-effectively.
DE 100 10 621 B4 discloses a method for quickly locating address blocks in grayscale images, which method is based on the finding that text generally contains both horizontally dominant and vertically dominant points in approximately equal values. Text kernels are marked in the method which comprise a group of starting points in fixed mutual proximity, there being for each starting point at least one horizontally dominant point and at least one vertically dominant point. This text kernel is then used to undertake an OCR detection. The grayscale image is acquired by means of a line camera in this method.
DE 195 32 342 C1 discloses an imaging system for automatic address detection on large letters and parcels with the aid of a high-resolution grayscale value camera and a low-resolution color camera. Both cameras are aligned with a light slit past which the object to be processed is guided. The color camera is operated in a special mode which enables the use of only one common light slit, an adequate light intensity being provided for both cameras. The signal of the multiplicity of elements of a color picture line is integrated over time and electronically averaged after the exposure. However, this design is comparatively expensive.
DE 10 2004 020 034 A1 discloses a scanner for digitally reading a newspaper which is deposited on an original table. A camera module has two sensors directed onto the original table and on which a region of the original table is respectively imaged via an optical system. Furthermore provided is an illuminating module which has at least two illuminating units which are arranged in parallel with a connecting line of the sensors on opposite sides of the camera module and are directed onto the original table. The aim of this is to realize homogeneous illumination of the original newspaper. In order further to homogenize illumination, it is possible for camera and illumination modules to be moved in a secondary scanning direction parallel to the surface of the original table, the regions imaged on the sensors sweeping over at least one predetermined region on the original table. An exact alignment of the original is possible owing to the use of an original table with well-defined edges, as well as a lay-on edge.